BUG#21310 - Trees in SQL causing a "crashed" table with MyISAM storage engine

An update that used a join of a table to itself and modified the
table on one side of the join reported the table as crashed or
updated wrong rows.

Fixed by creating temporary table for self-joined multi update statement.


mysql-test/r/myisam.result:
  A test case for BUG#21310.
mysql-test/t/myisam.test:
  A test case for BUG#21310.
sql/lock.cc:
  Exclude 'table' param from check.
sql/sql_update.cc:
  Disabling record cache for self-joined multi update statement is wrong.
  The join must only see the table as it was at the beginning of the statement.
  safe_update_on_fly check if it is safe to update first table on the fly, that is
  not creating temporary table. It is possible in case a row from this table is
  never read more than once. safe_update_on_fly now detect self-joined table and
  refuse to update this table on the fly.

1 files changed, 16 insertions, 0 deletions

diff --git a/mysql-test/r/myisam.result b/mysql-test/r/myisam.result
index b34c127595f..73cee4835bf 100644
--- a/mysql-test/r/myisam.result
+++ b/mysql-test/r/myisam.result
@@ -944,3 +944,19 @@ select * from t1;
 a
 42
 drop table t1;
+CREATE TABLE t1(a VARCHAR(16));
+INSERT INTO t1 VALUES('aaaaaaaa'),(NULL);
+UPDATE t1 AS ta1, t1 AS ta2 SET ta1.a='aaaaaaaaaaaaaaaa';
+SELECT * FROM t1;
+a
+aaaaaaaaaaaaaaaa
+aaaaaaaaaaaaaaaa
+DROP TABLE t1;
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES(1),(2);
+UPDATE t1,t1 AS t2 SET t1.a=t1.a+2 WHERE t1.a=t2.a-1;
+SELECT * FROM t1 ORDER BY a;
+a
+2
+3
+DROP TABLE t1;